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Controlled laboratory studies showed that the toxicity induced by biologically
relevant trace metal species of Cu, Cd, Pb and Zn on embryo-larval development occurred
at concentrations in excess of those found in the natural environinent, except for Cu in
metal perturbed areas. Average free ion concentrations inducing 50% abnormal
development( EC50feew) ere determineda s 0.23 nM CU2+8, 8.0 rim Cd2+,1 28 nM Zn2+a nd
3 62 nM Pb 2+
.
However, the response to some binary metal combinations indicated
enhanced (synergy) toxicity at concentrations relevant for estuarine waters (e. g. EC5of'. for
Cu2+i n the presenceo f C(ý: +, Zn2+a nd Pb2 +w as 0.004,0.02 and 0.04 nM, respectively).
A comparison of voltarnmetric instrumentation (voltammetric in situ profiling
(VIP) system versus Hanging Mercury Drop Electrode with potentiostat) highlighted the
advantage of high resolution measurements (ca. 20-60 min intervals) for environmental
studies and the minimisation of artefacts associated with discrete sampling methodologies.
Field-based studies were carried out in two contrasting estuaries in SW England,
one heavily impacted with metal contaminants (Fal Estuary) and another subject to greater
variety of anthropogenic influences (Tamar Estuary). High resolution in situ trace metal
speciationm easurementsc, arried out over tidal cycles, identified important information on
the temporal and spatial distributions of biologically relevant dynamic (<4 nm) metal
species of Cd, Pb and Cu. Variation in embryo-larval responses to discrete samples from
these estuaries, effectively paralleled the metal speciation measurements showing
enhanced toxicity when the marine water influence was at its lowest. In both systems, the
results indicated that the combined effect of the metals studied was likely to have provided
a significant contribution to the bioassay response. However, the difficulty in de-coupling
the speciation measurements with biological responses was evident and supports the need
for more comprehensive campaigns to study the impact of contaminants on ecosystem
functioning. Bioassay and metal speciation analysis techniques were complementary,
exhibiting high sensitivity and rapid responses, and would be considered effective
screening tools for waters subject to intermittent inputs of metal contaminants and areas
with recognised pressures. The integrated approach has extended our knowledge of trace
metal speciation in estuarine environments and their effects on the developing embryos of
the Pacific oyster. This approach has the potential for wider application.

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Access to the full-text thesis is no longer available at the author's request, due to 3rd party copyright restrictions. Access removed on 28.11.2016 by CS (TIS).

Metadata merged with duplicate record (http://hdl.handle.net/10026.1/2252) on 20.12.2016 by CS (TIS).

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Author manuscripts deposited to comply with open access mandates are made available in accordance with
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sought from the publisher or author.